Overexpression of transforming growth factor-beta is associated with increased hyaluronan content and impairment of repair in Marfan syndrome aortic aneurysm

Background-Marfan syndrome (MFS), a condition caused by fibrillin-1 gene mutation is associated with aortic aneurysm that shows elastic lamellae disruption, accumulation of glycosaminoglycans, and vascular smooth muscle cell (VSMC) apoptosis with minimal inflammatory response. We examined aneurysm tissue and cultured cells for expression of transforming growth factor-beta1 to -beta3 (TGF beta 1 to 3), hyaluronan content, apoptosis, markers of cell migration, and infiltration of vascular progenitor cells (CD34). Methods and Results-MFS aortic aneurysm (6 males, 5 females; age 8 to 78 years) and normal aorta (5 males, 3 females; age 22 to 56 years) were used. Immunohistochemistry showed increased expression of TGF beta 1 to 3, hyaluronan, and CD34-positive microcapillaries in MFS aneurysm compared with control. There was increased expression of TGF beta 1 to 3 and hyaluronan in MFS cultured VSMCs, adventitial fibroblasts (AF), and skin fibroblasts (SF). Apoptosis was increased in MFS (VSMC: mean cell loss in MFS 29%, n of subjects = 5, versus control 8%, n = 3, P < 0.05; AF: 28%, n = 5 versus 7%, n = 5, P < 0.05; SF: 29%, n = 3 versus 4%, n = 3, not significant). In MFS, there was a 2-fold increase in adventitial microcapillaries containing CD34-positive cells compared with control tissue. Scratch wound assay showed absence of CD44, MT1-MMP, and beta-3 integrin at the leading edge of migration in MFS indicating altered directional migration. Western blot showed increased expression of TGF beta 1 to 3 in MFS but no change in expression of CD44, MT1-MMP, or beta-3 integrin compared with controls. Conclusions-There was overexpression of TGF-beta in MFS associated with altered hyaluronan synthesis, increased apoptosis, impaired progenitor cell recruitment, and abnormal directional migration. These factors limit tissue repair and are likely to contribute to aneurysm development.

Inhibition of transforming growth factor-beta 1 signaling attenuates ataxia telanglectasia mutated activity in response to genotoxic stress

Ionizing radiation causes DNA damage that elicits a cellular program of damage control coordinated by the kinase activity of ataxia telangiectasia mutated protein (ATM). Transforming growth factor beta (TGF beta)-1, which is activated by radiation, is a potent and pleiotropic mediator of physiologic and pathologic processes. Here we show that TGF beta inhibition impedes the canonical cellular DNA damage stress response. Irradiated Tgf beta 1 nail murine epithelial cells or human epithelial cells treated with a small-molecule inhibitor of TGF beta type I receptor kinase exhibit decreased phosphorylation of Chk2, Rad17, and p53; reduced gamma H2AX radiation-induced foci; and increased radiosensitivity compared with TGF beta competent cells. We determined that loss of TGF beta signaling in epithelial cells truncated ATM autophosphorylation and significantly reduced its kinase activity, without affecting protein abundance. Addition of TGF beta restored functional ATM and downstream DNA damage responses. These data reveal a heretofore undetected critical link between the microenvironment and ATM, which directs epithelial cell stress responses, cell fate, and tissue integrity. Thus, Tgf beta 1, in addition to its role in homoeostatic growth control, plays a complex role in regulating responses to genotoxic stress, the failure of which would contribute to the development of cancer; conversely, inhibiting TGF beta may be used to advantage in cancer therapy.

Do changes in transglutaminase activity alter latent transforming growth factor beta activation in experimental diabetic nephropathy?

Background. Diabetic nephropathy is the leading cause of end-stage kidney failure worldwide. It is characterized by excessive extracellular matrix accumulation. Transforming growth factor beta 1 (TGF-ß1) is a fibrogenic cytokine playing a major role in the healing process and scarring by regulating extracellular matrix turnover, cell proliferation and epithelial mesanchymal transdifferentiation. Newly synthesized TGF-ß is released as a latent, biologically inactive complex. The cross-linking of the large latent TGF-ß to the extracellular matrix by transglutaminase 2 (TG2) is one of the key mechanisms of recruitment and activation of this cytokine. TG2 is an enzyme catalyzing an acyl transfer reaction leading to the formation of a stable e(?-glutamyl)-lysine cross-link between peptides.Methods. To investigate if changes in TG activity can modulate TGF-ß1 activation, we used the mink lung cell bioassay to assess TGF-ß activity in the streptozotocin model of diabetic nephropathy treated with TG inhibitor NTU281 and in TG2 overexpressing opossum kidney (OK) proximal tubular epithelial cells.Results. Application of the site-directed TG inhibitor NTU281 caused a 25% reduction in kidney levels of active TGF-ß1. Specific upregulation of TG2 in OK proximal tubular epithelial cells increased latent TGF-ß recruitment and activation by 20.7% and 19.7%, respectively, in co-cultures with latent TGF-ß binding protein producing fibroblasts.Conclusions. Regulation of TG2 directly influences the level of active TGF-ß1, and thus, TG inhibition may exert a renoprotective effect by targeting not only a direct extracellular matrix deposition but also TGF-ß1 activation and recruitment.

Understanding the role of transforming growth factor beta signalling and epigenomics in osteoarthritis

Osteoarthritis (OA) is the most common form of arthritis with a high socioeconomic burden, with an incompletely understood etiology. Evidence suggests a role for the transforming growth factor beta (TGF-ß) signalling pathway and epigenomics in OA. The aim of this thesis was to understand the involvement of the TGF-ß pathway in OA and to determine the DNA methylation patterns of OA-affected cartilage as compared to the OA-free cartilage. First, I found that a common SNP in the BMP2 gene, a ligand in the Bone morphogenetic protein (BMP) subunit of TGF-ß pathway, was associated with OA in the Newfoundland population. I also showed a genetic association between SMAD3 - a signal transducer in the TGF-ß subunit of the TGF-ß signalling pathway - and the total radiographic burden of OA. I further demonstrated that SMAD3 is over-expressed in OA cartilage, suggesting an over activation of the TGF-ß signalling in OA. Next, I examined the connection of these genes in the regulation of matrix metallopeptidase 13 (MMP13) - an enzyme known to destroy extracellular matrix in OA cartilage - in the context of the TGF-ß signalling. The analyses showed that TGF-ß, MMP13, and SMAD3 were overexpressed in OA cartilage, whereas the expression of BMP2 was significantly reduced. The expression of TGF-ß was positively correlated with that of SMAD3 and MMP13, suggesting that TGF-ß signalling is involved in up-regulation of MMP13. This regulation, however, appears not to be controlled by SMAD3 signals, possibly due to the involvement of collateral signalling, and to be suppressed by BMP regulation in healthy cartilage, whose levels were reduced in end-stage OA. In a genome-wide DNA methylation analysis, I reported CpG sites differentially methylated in OA and showed that the cartilage methylome has a potential to distinguish between OA-affected and non-OA cartilage. Functional clustering analysis of the genes harbouring differentially methylated loci revealed that they are enriched in the skeletal system morphogenesis pathway, which could be a potential candidate for further OA studies. Overall, the findings from the present thesis provide evidence that the TGF-ß signalling pathway is associated with the development of OA, and epigenomics might be involved as a potential mechanism in OA.

Rôle du facteur de croissance transforming growth factor beta-1 (TGF[beta]1) dans la synthèse d'oestradiol par les follicules ovariens bovins

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Rôle du facteur de croissance transforming growth factor beta-1 (TGF[beta]1) dans la synthèse d'oestradiol par les follicules ovariens bovins

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Extracellular matrix sub-types and mechanical stretch impact human cardiac fibroblast responses to transforming growth factor beta

Understanding the impact of extracellular matrix sub-types and mechanical stretch on cardiac fibroblast activity is required to help unravel the pathophysiology of myocardial fibrotic diseases. Therefore, the purpose of this study was to investigate pro-fibrotic responses of primary human cardiac fibroblast cells exposed to different extracellular matrix components, including collagen sub-types I, III, IV, VI and laminin. The impact of mechanical cyclical stretch and treatment with transforming growth factor beta 1 (TGFβ1) on collagen 1, collagen 3 and alpha smooth muscle actin mRNA expression on different matrices was assessed using quantitative real-time PCR. Our results revealed that all of the matrices studied not only affected the expression of pro-fibrotic genes in primary human cardiac fibroblast cells at rest but also affected their response to TGFβ1. In addition, differential cellular responses to mechanical cyclical stretch were observed depending on the type of matrix the cells were adhered to. These findings may give insight into the impact of selective pathological deposition of extracellular matrix proteins within different disease states and how these could impact the fibrotic environment.

Interleukin 1 beta suppresses transforming growth factor-induced inorganic pyrophosphate (PPi) production and expression of the PPi-generating enzyme PC-1 in human chondrocytes.

Articular cartilage chondrocytes have the unique ability to elaborate large amounts of extracellular pyrophosphate (PPi), and transforming growth factor beta (TGF beta) appears singular among cartilage regulatory factors in stimulating PPi production. TGF beta caused a time and dose-dependent increase in intracellular and extracellular PPi in human articular chondrocyte cultures. TGF beta and interleukin 1 beta (IL-1 beta) antagonistically regulate certain chondrocyte functions. IL-1 beta profoundly inhibited basal and TGF beta-induced PPi elaboration. To address mechanisms involved with the regulation of PPi synthesis by IL-1 beta and TGF beta, we analyzed the activity of the PPi-generating enzyme NTP pyrophosphohydrolase (NTPPPH) and the PPi-hydrolyzing enzyme alkaline phosphatase. Human chondrocyte NTPPPH activity was largely attributable to plasma cell membrane glycoprotein 1, PC-1. Furthermore, TGF beta induced comparable increases in the activity of extracellular PPi, intracellular PPi, and cellular NTPPPH and in the levels of PC-1 protein and mRNA in chondrocytes as well as a decrease in alkaline phosphatase. All of these TGF beta-induced responses were completely blocked by IL-1 beta. Thus, IL-1 beta may be an important regulator of mineralization in chondrocytes by inhibiting TGF beta-induced PPi production and PC-1 expression.

Glycosaminoglycan and growth factor mediated murine calvarial cell proliferation

Understanding the complex mechanisms underlying bone remodeling is crucial to the development of novel therapeutics. Glycosaminoglycans (GAGs) localised to the extracellular matrix (ECM) of bone are thought to play a key role in mediating aspects of bone development. The influence of isolated GAGs was studied by utilising in vitro murine calvarial monolayer and organ culture model systems. Addition of GAG preparations extracted from the cell surface of human osteoblasts at high concentrations (5 microg/ml) resulted in decreased proliferation of cells and decreased suture width and number of bone lining cells in calvarial sections. When we investigated potential interactions between the growth factors fibroblast growth factor-2 (FGF2), bone morphogenic protein-2 (BMP2) and transforming growth factor-beta1 (TGFbeta1) and the isolated cell surface GAGs, differences between the two model systems emerged. The cell culture system demonstrated a potentiating role for the isolated GAGs in the inhibition of FGF2 and TGFbeta1 actions. In contrast, the organ culture system demonstrated an enhanced stimulation of TFGbeta1 effects. These results emphasise the role of the ECM in mediating the interactions between GAGs and growth factors during bone development and suggest the GAG preparations contain potent inhibitory or stimulatory components able to mediate growth factor activity.

Repeated intrauterine exposures to inflammatory stimuli attenuated transforming growth factor-β signaling in the ovine fetal lung

Background: Bronchopulmonary dysplasia (BPD) is one of the most common complications after preterm birth and is associated with intrauterine exposure to bacteria. Transforming growth factor-β (TGFβ) is implicated in the development of BPD. Objectives: We hypothesized that different and/or multiple bacterial signals could elicit divergent TGFβ signaling responses in the developing lung. Methods: Time-mated pregnant Merino ewes received an intra-amniotic injection of lipopolysaccharide (LPS) and/or Ureaplasma parvum serovar 3 (UP) at 117 days' and/or 121/122 days' gestational age (GA). Controls received an equivalent injection of saline and or media. Lambs were euthanized at 124 days' GA (term = 150 days' GA). TGFβ1, TGFβ2, TGFβ3, TGFβ receptor (R)1 and TGFβR2 protein levels, Smad2 phosphorylation and elastin deposition were evaluated in lung tissue. Results: Total TGFβ1 and TGFβ2 decreased by 24 and 51% after combined UP+LPS exposure, whereas total TGFβ1 increased by 31% after 7 days' LPS exposure but not after double exposures. Alveolar expression of TGFβR2 decreased 75% after UP, but remained unaltered after double exposures. Decreased focal elastin deposition after single LPS exposure was prevented by double exposures. Conclusions: TGFβ signaling components and elastin responded differently to intrauterine LPS and UP exposure. Multiple bacterial exposures attenuated TGFβ signaling and normalized elastin deposition.

Interleukin-1β stimulates human renal fibroblast proliferation and matrix protein production by means of a transforming growth factor-β-dependent mechanism

One of the hallmarks of progressive renal disease is the development of tubulointerstitial fibrosis. This is frequently preceded by macrophage infiltration, raising the possibility that macrophages relay fibrogenic signals to resident tubulointerstitial cells. The aim of this study was to investigate the potentially fibrogenic role of interleukin-1beta (IL-1beta), a macrophage-derived inflammatory cytokine, on cortical fibroblasts (CFs). Primary cultures of human renal CFs were established and incubated for 24 hours in the presence or absence of IL-1beta. We found that IL-1beta significantly stimulated DNA synthesis (356.7% +/- 39% of control, P <.003), fibronectin secretion (261.8 +/- 11% of control, P <.005), collagen type 1 production, (release of procollagen type 1 C-terminal-peptide, 152.4% +/- 26% of control, P <.005), transforming growth factor-beta (TGF-beta) secretion (211% +/- 37% of control, P <.01), and nitric oxide (NO) production (342.8% +/- 69% of control, P <.002). TGF-beta (1 ng/mL) and the phorbol ester phorbol 12-myristate 13-acetate (PMA, 25 nmol/L) produced fibrogenic effects similar to those of IL-1beta. Neither a NO synthase inhibitor (N(G)-methyl-l-arginine, 1 mmol/L) nor a protein kinase C (PKC) inhibitor (bis-indolylmaleimide 1, 1 micromol/L) altered the enhanced level of fibronectin secretion or DNA synthesis seen in response to IL-1beta treatment. However, addition of a TGF-beta-neutralizing antibody significantly reduced IL-1beta-induced fibronectin secretion (IL-1beta + IgG, 262% +/- 72% vs IL-1beta + alphaTGF-beta 156% +/- 14%, P <.02), collagen type 1 production (IL-1beta + IgG, 176% +/- 28% vs IL-1beta + alphaTGF-beta, 120% +/- 14%, P <.005) and abrogated IL-1beta-induced DNA synthesis (245% +/- 49% vs 105% +/- 21%, P <.005). IL-1beta significantly stimulated CF DNA synthesis and production of fibronectin, collagen type 1, TGFbeta, and NO. The fibrogenic and proliferative action of IL-1beta on CF appears not to involve activation of PKC or production of NO but is at least partly TGFbeta-dependent.

The effect of transforming growth factor β1 gene polymorphisms in ankylosing spondylitis

Objectives. To determine whether genetic polymorphisms in or near the transforming growth factor β1 (TGFB1) locus were associated d with susceptibility to or severity of ankylosing spondylitis (AS). Methods. Five intragenic single-nucleotide polymorphisms (SNP) and three microsatellite markers flanking the TGFB1 locus were genotyped. Seven hundred and sixty-two individuals from 184 multiplex families were genotyped for the microsatellite markers and two of the promoter SNPs. One thousand and two individuals from 212 English and 170 Finnish families with AS were genotyped for all five intragenic SNPs. A structured questionnaire was used to assess the age of symptom onset, disease duration and disease severity scores, including the BASDAI (Bath Ankylosing Spondylitis Disease Activity Index) and BASFI (Bath Ankylosing Spondylitis Functional Index). Results. A weak association was noted between the rare TGFB1 + 1632 T allele and AS in the Finnish population (P = 0.04) and in the combined data set (P = 0.03). No association was noted between any other SNPs or SNP haplotype and AS, even among those families with positive non-parametric linkage scores. The TGFB1 +1632 polymorphism was also associated with a younger age of symptom onset (English population, allele 2 associated with age of onset greater by 4.2 yr, P = 0.05; combined data set, allele 2 associated with age of onset greater by 3.2 yr, P = 0.02). A haplotype of coding region SNPs (TGFB1 +869/ +915+1632 alleles 2/1/2) was associated with age of symptom onset in both the English parent-case trios and the combined data set (English data set, haplotype 2/1/2 associated with age of onset greater by 4.9 yr, P = 0.03; combined data set, haplotype 2/1/2 associated with greater age of onset by 4.2 yr, P = 0.006). Weak linkage with AS susceptibility was noted and the peak LOD score was 1.3 at distance 2 cM centromeric to the TGFB1 gene. No other linkage or association was found between quantitative traits and the markers. Conclusion. This study suggests that the polymorphisms within the TGFB1 gene play at most a small role in AS and that other genes encoded on chromosome 19 are involved in susceptibility to the disease.